Selenium (Se) is one of the most volatile trace metals emitted from coal-fired combustors and will most probably be considered for regulation in the electric power industry due to its significant environmental impact. Novel technologies are needed to remove Se vapor. This requires first a clear understanding of the behavior of selenium in combustion. In this work, coal and coke samples spiked with Se were prepared and the effect of Se on combustion was evaluated in a thermobalance. Impregnation with Se had a negligible impact on the combustion of coke; this allowed a systematic experimental study of the vaporization, condensation, and association of Se through burning cokes spiked with Se. Capturing the aerosol in the combustion flue gas on a membrane filter, coupled with identification of the species present using X-ray photoelectron spectroscopy, was established as a useful approach for coal combustion. The high volatility of Se and its affinity for oxygen, as well as the effect of chlorine on its vaporization, supported our previous calculations. The dominant Se species were identified as atomic Se and SeO 2 , which also confirmed the thermodynamic predictions.